Cellulosic product



May 29, 1962 E. H. VOIGTMAN ET AL CELLULOSIC PRODUCT Filed April 10, 1957 INVENTORS. :MJ/ Z Q jut M, M,JMA 8 United States Patent @tifiee dfidbfii Patented i i-Kay 29, 19 52 3,036,573 CELLULOSIC PRODUCT Edward H. Voigtman and Richard A. Woiterding, Neenah, Wis, assignors to Kirnheriy-Ciark Corporation, Neenah, Win, a corporation of Delaware Filed Apr. 10, 1957, Ser. No. 651,955 3 Claims. (Cl. 12829d) The present invention relates generally to cellulosic products and is more particularly directed to an improved form of disposable diaper.

Various forms of disposable diapers have been devised heretofore and the need for such a product is evidenced by the large number of disposable diapers currently being marketed. Generally, the disposable diapers found on the market, as well as many of those in the prior art which are not available commercially, comprise for the main part an absorbent section of creped wadding or the like held within a suitable wrapper which extends either partially or entirely around the absorbent section.

Although the known forms of disposable diapers have been found to be useful to the extent that some have been commercially accepted, even the most acceptable have been lacking in certain desired characteristics, which makes the use of such diapers not too satisfactory. One of the more objectionable features of the known disposable diaper constructions is the general tendency for the diaper to become compressed, particularly in the region between the infants thighs, and to readily disintegrate when the diaper is wetted. Then too, generally only a small percentage of the absorbency available in the diaper material is effectively used, due primarily to the arrangement and construction of the absorbent material used in the known form of disposable diapers.

It is the principal object of the present invention to provide an improved form of disposable diaper, which is particularly resistant to becoming compacted into a dense mass and disintegrating when in use. Another object is to provide a disposable diaper, which includes a novel means for controlling fluid flow in the diaper so as to utilize a maximum amount of the absorptive capacity of the diaper. Still another object of the invention is to provide a disposable diaper having the foregoing features, which has the absorbent portion of the diaper arranged to provide the greatest amount of absorbency where needed and to enable the diaper to conform more readily to the body.

Other objects and advantages will be noted with referenc to the accompanying illustrations and description of selected embodiments of the invention.

In the drawings:

FIGURE 1 is a schematic showing of one embodiment of the invention, in perspective;

FIGURE 2 is an enlarged fragmentary sectional view, taken along line 22 in FIGURE 1, schematically illustrating the structural arrangement for the principal embodiment of the invention;

FIGURE 3 is a perspective view of another embodiment of the invention;

FIGURE 4 is an enlarged fragmentary sectional view, taken along the line 4-4 in FIGURE 3;

FIGURE 5 is an enlarged fragmentary sectional view of another modification of the invention.

Generally, certain of the above-stated objects of this invention are accomplished by advantageously using a Wet-strength sheet adjacent the top of the absorbent section of the diaper. This arrangement is particularly effective in distributing fluid throughout the absorbent section of the diaper and in preventing the absorbent section from becoming compressed and forming a compact wad when wetted, Moreover, one form of the invention contemplates the formation of such a disposable diaper from generally uniform width plies of absorbent material, which are arranged in a novel manner so as to provide the major portion of the absorbent material at the central section of the diaper, where it is more advantageously utilized, and to provide a lesser thickness of material adjacent the edges of the diaper to thereby enable the diaper to more easily conform with the body and to facilitate pinning the diaper in place. Then too, one aspect of the invention includes the use of wet-strength fluid permeable sheets as top and bottom sheets for an absorbent section of fluff or loose fibrous material, in order to more uniformly distribute fluid to the fluff and retain the latter in position within the diaper.

With reference particularly to FIGURES l and 2, it is seen that one embodiment of the invention comprises a diaper it) having an absorbent section formed of a plurality of plies of absorbent sheet material 12, such as creped wadding. The diaper also includes a fluid permeable' sheet 14 having wet strength, which is disposed on top of the absorbent sheets 12, a fluid-permeable top sheet or cover 16 of relatively strong fibrous material, such as a non-woven fibrous web, and a bottom sheet 18 of fluid impermeable material which provides the outer layer or backing for the diaper. The bottom sheet 18 is preferably folded along its side edges in overlapping relation to the top web and is suitably bonded thereto, as by heat sealing the two sheets together.

With the diaper construction just described, there is particular advantage with respect to the stability of the diaper when Wetted. The disposition of the wet strength, fluid permeable sheet 14 intermediate the porous top sheet 16 and the main absorbent section 12 is a primary factor in affording this advantage. The Wet strength sheet 14 not only lends strength to the uppermost or inwardly facing surface of the diaper, but it also serves as a means for more uniformly distributing fluids, so that the fluids are not concentrated in the region of initial contact with the diaper but flow laterally in all directions as they move downwardly into the absorbent section 12 of the diaper. With this distribution of the fluids, the tendency of a localized area of the absorbent section to become compacted and ball up is avoided. Further, with the more uniform distribution of the fluids and the greater strength afforded for the surface of the absorbent section by the wet-strength sheet, the absorbent material remains intact and the normal tendency of such material to disintegrate when wetted is overcome.

Then too, the envelope or wrapper provided by the fluid impermeable backing sheet 18 and the top porous sheet 16 afiords additional means for stabilizing the absorbent material and retaining the general shape of the diaper during use. It will be understood, of course, that the illustrations of the diaper construction are schematic in nature, in order to best illustrate the arrangement of the diaper components. All of the components being very flexible, the diaper is in fact quite limp and readily conformable to the body, and it will not, of course, have the truiy rectangular cross-sectional shape shown in the drawings but will tend to flatten out along the edges.

In a preferred form of the diaper shown in FIGURES l and 2, the top sheet 16 is a cross-laid, n1ulti-filament thread web with a lightweight fiber web or applique attached to the upper surface, such as is shown in the Harwood application Serial No. 459,473, issued August 25, 1959 as United States Letters Patent No. 2,900,980 which is also assigned to the assignee of this invention. Of course, other porous webs such as gauze may be used for the diaper top sheets. The sheet 14 immediately underiying the top or cover sheet 16 may be a fluid permeable wet strength sheet of creped wadding. A suitable sheet is made from percent chemical wood pulp and having a dryer basis weight of 5 pounds per standard ream of 480 sheets 24 x 36 inches and a crepe ratio of 2. A suitable wet strength resin such as melamine formaldehyde is added to the sheet in an amount of about 1.5 percent by weight of the dry pulp. Generally, sheets having a dryer basis weight of within about 4.5 to 9.0 pounds per standard ream and a crepe ratio within the range of 1.25 to 3.0 will provide a satisfactory base sheet for the wet strength sheet. Further, other types of wet strength resins, including urea formaldehyde, may be used in quantities ranging from about 1.5 to 3.0 percent of the weight of the dry pulp. It will also be understood that the base sheet for the wet strength sheet may contain cellulosic fibers, synthetic fibers, thermoplastic fibers, or blends of fibers formed to provide a fluid permeable sheet.

The absorbent section 12 for the diaper is formed from about plies of creped wadding sheet material, which is preferably made of chemical wood pulp and has a dryer basis weight of about 5 pounds per standard ream and a crepe ratio of about 2. However, it is believed that other satisfactory diapers might be made in accordance with the principles of this invention, which include an absorbent section of from about 6 to sheets of creped wadding having a dryer basis weight within the range of about 4.5 to 9.0 pounds per standard ream and a crepe ratio of from about 1.25 to 3.0. In the event that more than about 10 plies or sheets are used, it is believed that it is advantageous to include in the diaper an additional wet strength sheet at a position between the absorbent section 12 and the fluid impermeable bottom sheet 18.

The bottom sheet 18 is preferably a very thin and flexible, fluid impermeable sheet, such as a polyethylene sheet having a thickness of about .001 inch. The sheet should be very flexible and strong enough to receive a pin therethrough without tearing. Although moisture resistant sheets other than thermoplastic sheets may be use for the bottom sheet, thermoplastic material is advantageous in that it permits a bonding thereof with the top sheet, as by heat sealing the two sheets together along opposite edges of the diaper. Other fluid impervious sheets having suificient strength and flexibility, such as Mylar, a product of E. I. du Pont de Nemours & (30., might be used. In using thermoplastic sheet material, it is believed that a thickness of between .0002 and .002 inch for such sheet will prove satisfactory.

Additional advantages will be gained by employing a germicidal or antiseptic agent in the diaper by treating one or more sheets of the diaper material with such agent. The treated sheet should preferably be near the top or inwardly facing surface of the diaper, preferably the sheet immediately below the wet strength sheet 14, although it may be the latter. In this connection, satisfactory results have been obtained by using .6 percent by weight of di-isobutyl cresoXy ethoxy ethyl dimethyl benzyl ammonium chloride. Other compounds are, of course, suitable for this use, such as those described in DeWet Patent 2,634,229. In using quaternary ammonium compounds, an amount of between .3 to 1 percent, by weight, is believed sufliciently effective.

Another embodiment of this invention is seen in EEG- URES 3 and 4, wherein there is illustrated a disposable diaper 21 having a top sheet 22, a bottom sheet 24, and an absorbent section having a plurality of plies 26 of absorbent sheet material disposed between a pair of wet strength absorbent sheets 23. A fluid repellant bafile sheet 30 is disposed intermediate the plies of absorbent sheet material, preferably mid-Way between the plies. Furthermore, it will be noted that the absorbent plies 26 and the baflle sheet 30 are disposed in staggered relation to each other, in order to thereby present an ab sorbent section which is relatively thicker at the center and which tapers toward the outer edges of the diaper. This arrangement is particularly advantageous in that it provides the greatest amount of absorbent material where tit i needed, and it reduces the thickness of the side edges to enable the diaper to more easily conform to the body and to permit easier pinning of the diaper in place.

Although the top sheet 22 may be of any soft, nonchafing porous material which will not disintegrate when wetted, the preferred embodiment of the diaper shown in FIGURES 3 and 4 utilizes a gauze sheet having a fiber applique on the upper surface. A more detailed description of this material will be found in the Harwood Patent No. 2,777,779, issued January 15, 1957 and assigned to the assignee of the present invention.

The bottom sheet 24 is, of course, a flexible fluid-impervious material and maybe a polyethylene sheet, such as is described above with respect to FIGURE 2. It will be noted that in the embodiment of FIGURE 4, the bottom sheet 24 is shown as being attached to the underside of the top sheet 22, as by heat sealing or the like. Of course, the arrangement shown in FIGURE 2, in this respect, may be used, as well as other suitable modes of accomplishing the desired attachment.

The pair of wet strength sheets 28 are preferably of the type described above and are disposed, respectively, intermediate the top sheet 22 and the upper ply of the absorbent section 26 and between the fluid-impervious bottom sheet 24 and the bottom ply of the absorbent section. This arrangement affords more uniform distribution of fluid flow, avoids saturation of the bottom ply with fluids after the latter have penetrated the absorbent section, and prevents disintegration of the absorbent plies when wetted. The use of two wet strength sheets in this manner is particularly effective in a thicker pad or diaper. The bottom wet strength sheet 28 helps to distribute fluid which may penetrate the absorbent section and which would otherwise tend to saturate a local area rather than flow out into other regions of the diaper. While the Wet strength sheets 28 should be flexible and soft, it is preferred that they have suflicient surface irregularities to provide a frictional engagement with the adjacent absorbent plies, to thereby assist in maintaining the diaper components in position with respect to each other. This can be achieved in any suitable manner, such as creping the sheet, needling, embossing, etc.

The absorbent section 26 of the diaper is preferably formed of a plurality of creped wadding sheets, as described with respect to FIGURE 1. The sheets are of uniform size but have a width substantially less than the width of the completed diaper, preferably about two-thirds the total width of the diaper. For example, in a diaper having a width of 13 inches, each of the absorbent plies has a width of about 8.5 inches. As seen in FIGURE 4, the successive plies are laterally displaced with respect to each other along opposite edges, in order to thereby provide a cross-section of parallelogram form. With this arrangement, the central section of about 4.3 inches in width includes the combined thickness of all the plies of absorbent material, and the outer one-third portions of the diaper diminish in thickness or taper toward each side edge. Consequently, the major portion of the absorbent material is disposed in the normal area of initial fluid contact, where it is most necessary, and the outer edges of the diaper, which receive less fluid, are made more flexible and conformable to the body. Of course, other arrangements for presenting a major portion of the absorbent material near the center of the diaper may be used in combination with the disclosed use of a wet strength sheet in order to enjoy the advantages of the latter feature of this invention.

The fluid retardant baffle sheet 30 is disposed intermediate the plies of absorbent sheet material 26, primarily to provide for greater utilization of the effective absorbent capacity of the absorbent section 26' by retarding the flow of fluid through the thickness of this section. With the baflle sheet 30 in the diaper, there is a greater tendency for the fluids to be distributed along the length and width of the diaper 20 before proceeding through the entire thickness of the absorbent section. Thus, there is prevented any concentration of the fluid flow, which otherwise usually occurs and results in wetting through a localized area of the diaper without utilizing the absorbency of a major portion of the diaper. It is this concentration of fluids which frequently causes the central section of the diaper to become compacted and to disintegrate under the forces created upon motion of the body.

The baflie sheet 30 may be any suitable sheet material, which is capable of retarding fluid flow by virtue of its being less porous and less absorbent than the material used in the absorbent section of the diaper. For example, it can be a creped wadding sheet, treated or untreated for wet strength, which is lightly waxed so as to diminish the porosity and absorbency of the sheet. Then too, the desired effect can also be achieved by using one or m re sheets of creped wadding or the like which are embossed.

In a particular embodiment of the diaper seen in FIG- URES 3 and 4, a satisfactory baffle sheet was made by applying from 3 to 5 percent by weight of 153 C. wax to a creped wadding sheet having a basis weight of about 5 pounds per standard ream of 480 sheets 24 x 36 inches and a crepe ratio of 2. The top sheet 22 for the diaper 21 was a gauze sheet with a fiber applique, which is referred to above. The wet strength sheets 28, absorbent section plies 26, and the bottom sheet 24 were the same material as those described in the specific example of FIGURE 2.

Still another embodiment of this invention is shown in FIGURE 5, wherein the absorbent section of the diaper 31 includes a central layer 32 of fluff and a plurality of plies of absorbent sheets 34, one or more of which are treated with an antiseptic or deodorant. As in the previous embodiments, the diaper 31 also includes a porous top sheet 36 of suitable material which will not disintegrate under ordinary conditions of use, and a bottom sheet 38 of fluid impervious and relatively thin material which extends at opposite edges of the diaper in overlapping relation to the top sheet and is suitably bonded thereto, as by heat sealing.

There is also provided a Wet strength absorbent sheet 40 intermediate the top sheet 36 and the absorbent section. A second wet strength sheet indicated at 40a, may be advantageously used between the bottom sheet 38 and the absorbent section of the diaper, when a relatively thick absorbent section is used. The fluff 32, which is disposed between the plies of creped wadding, is dry, mechanically disintegrated wood pulp fiber reduced to individual fiber state, and this fluff preferably comprises approximately 50 percent, by weight, of the absorbent section. Preferably each of the two plies 34a and 34b adjacent the fluff section is a wet strength sheet. Further, one or both of these sheets 34a and 34b is preferably treated with an antiseptic or deodorant agent. There are many suitable available compounds for this purpose, such as those mentioned above.

It is seen, therefore, that there is provided herein a novel form of disposable diaper which, generally is characterized by the utilization of a wet strength sheet between the top sheet and the absorbent section, in order to equalize the flow of fluid throughout the diaper and prevent the diaper from balling up and disintegrating when wetted. Further, there is provided a diaper which conforms readily to the body, while holding the components in their relative positions, and which utilizes a maximum amount of the absorptive capacity of the diaper. In addition, the present invention contemplates the control of bacteria in the diaper to eliminate odors.

Although shown and described with respect to particular embodiments, it will be apparent that other modifications might be made without departing from the principles of this invention.

We claim:

1. A disposable diaper comprising a top sheet of soft, flexible fibrous material which is fluid permeable, an underlying wet-strength sheet of creped wadding, an absorbent section comprising a plurality of plies of creped wadding and including an intermediate baflie sheet for retarding the flow of fluid therethrough, said absorbent section being formed of plies of generally uniform width arranged in generally uniformly laterally displaced relation to one another so as to provide substantially greater bulk along the center of the diaper than at the side edges thereof, a second wet-strength sheet of creped wadding underlying said absorbent section, and a bottom sheet of flexible, fluid-impervious material having opposite side edges thereof folded over and secured in position between the side edges of said top and underlying sheets.

2. A disposable diaper comprising a porous top sheet of soft, flexible fibrous material, an underlying flexible, wet-strength sheet of fluid permeable material, an ab sorbent section comprising a plurality of plies of creped wadding including an intermediate baffle sheet of lesser absorbency for retarding the flow of fluid through said section, said absorbent section being formed of plies of generally uniform width arranged to provide a cross-section generally of parallelogram form so as to afford substantially greater bulk along the center section of the diaper than at the side edges thereof, a second wet-strength sheet of creped wadding underlying said absorbent section, and a bottom sheet of flexible, thermoplastic material having opposite side edges thereof folded over and heat sealed in position between the marginal side edges of said top and underlying sheets.

3. A disposable diaper comprising a porous top sheet of soft, flexible fibrous material, an underlying flexible wet strength sheet of fluid permeable material, an absorbent section comprising a plurality of plies of creped wadding and a section of fluff intermediate said plies of creped wadding and comprising about 50 percent, by weight, of the absorbent section, with the pair of plies of creped wadding immediately adjacent said fluff being treated for wet strength, another wet strength sheet of creped wadding underlying said absorbent section, and a bottom sheet of flexible, fluid-impermeable material having opposite edges thereof folded over and secured to said top sheet.

References Cited in the tile of this patent UNITED STATES PATENTS 2,062,978 King Dec. 1, 1936 2,464,640 Fourness Mar. 15, 1949 2,649,859 Hermanson et al Aug. 25, 1953 2,696,819 Lovekin Dec. 14, 1954 2,699,170 Morin -1 Jan. 11, 1955 2,815,027 Makela Dec. 3, 1957 2,833,283 Spahr et a1 May 6, 1958 2,916,037 Hansen Dec. 8, 1959 FOREIGN PATENTS 166,031 Australia Nov. 16, 1955 

